1. Field of the Invention
This invention is directed to counting devices, in general, and to high speed counting devices, in particular.
2. Prior Art
There are many counting circuits known in the art. These circuits are adapted to count various items, usually by means of counting pulses which are indicative of the items to be counted. The counters may operate on straight binary counting codes, Gray-codes or any other suitable code arrangement. In these known counters, the usual technique is to detect a pulse or the like to be counted and to serially operate thereon. That is, the detected pulse is added to (or subtracted from) the count which is currently extant. (Of course, in the case where the count is subtracted, the counter operates as a decrementer rather than an incrementer.)
The counters which are known in the art are of various configurations. Moreover, the counters utilize various types of logic construction techniques. Typically, the counters are formed of discrete components or integrated logic circuits but, frequently, can be modified and reduced to various types of LSI or VLSI techniques.
In many cases, the counters which are known in the art (whether incrementers or decrementers) tend to be relatively slow in operation thereby creating a certain amount of limitation on the operating speed of the overall circuit. Moreover, the propagation of the "carry-in" signal through the circuit is often-times a troublesome aspect which causes complications in the logic scheme. This is frequently the case, even in the so-called "carry-ripple" type circuits.